Resilient pitman bell crank



. Nov. 16, 1954 A. H. JOHNSON RESILIENT PITMAN BELL CRANK Filed Jan. 8,1951 3 Shets-Sheet l IIIIIU 3 rmentor NOV. 16, 1954 A, H JOHNSON2,694,319

RESILIENT PITMAN BELL CRANK Filed Jan. 8, 1951 3 Sheets-Sheet 2 3nventor Nov. 16, 1954 A. H. JOHNSQN RESILIENT PITMAN BELL CRANK 3sheetsesheet 3 Filed Jan. 8 1951 United States PatentO RESILIENT PITMANBELL CRANK Ax'el H. Johnson, Racine, Wis., assignor to' J. I. CaseCompany, Racine, Wis., a corporation of Wisconsin Application January 8,1951, Serial No. 204,862

7 Claims. (Cl. 74-559) This invention relates to harvesting machines'andespecially to the means for reciprocating the sickle attached to suchmachines. Specifically, this invention concerns an improvement in thebell crank employed to change the direction of actuation from afore-and-aft reciprocation to one transverse to the direction of travelof the machine.

An object of this invention is to provide a means of reducing the shockincident to the reciprocation of harvester machine sickles.

Another object is to simplify the construction of devices of this natureby adopting a construction in which duplicate parts are employed thussimplifying inventories and making for economy in manufacture.

Another object is to provide a device ofthis nature which can be made oflighter components thus directly reducing the reciprocating mass andthereby minimize the tendency for failure of various members in themachine owing to excessive vibration.

Another object is to provide a device whichwill be quiet in operationowing to an absence of vibration.

Another object is to provide a device of this nature which will have asmooth, more positive cutting action as a result of the absence ofvibration.

Further objects and advantages of the inventionwill become apparent froma consideration of the following detailed description taken inconnection with the accompanying drawing wherein a satisfactoryembodiment of the invention is shown. However, it is to be understoodthat the invention is not limited to the details disclosed but includesall such variations and modifications as fall within the spirit of theinvention.

A serious problem generally prevalent concerning drives forreciprocating sickles and similar devices is the damage caused byvibration. This damage generally increases as the rate of reciprocationincreases.

Damage to reciprocating mechanisms is mainly caused by the shockincident to the sudden reversal of direction of the various members. Thedamage takes on several forms, one being that bearings are quickly wornout of round with the result that the machine becomes noisy. Wornbearings encourage vibration which in turn causes wear in other parts ofthe implement.

Another form of damage prevalent in reciprocating mechanisms is thatcaused by bolts and other fastenings becoming loose which in turn resultin the loss of members of the implements. Such loss of one member maycause damage to another, even in remote portions of'the implement.

Vibration frequently interferes with the proper functioning of thesickle in that its cutting function is impaired, the vibrationpreventing continuous contact between the sickle and the knives.

It is believed that this invention reduces the vibration of the sickledrive of harvesters. mowers and the like by providing a bell crankarranged so that the shocks incident to this type of mechanism aresubstantially absorbed.

Referring to the drawings:

Fig. 1 shows a fragmentary front view of an element having parts brokenaway and showing the invention;

Fig. 2 shows a bell crank incorporating'the invention and detached fromthe implement;

Fig. 3 is a fragmentary view-of the lower support block for the bellcrank;

Fig. 4 is a plan viewof the upper crank arm;

Fig. '5 is an elevational' view ofthecrankarmeas':

shown in Fig. 4;

Fig. 6 is a modification ofthe bell crank shown inFigsa land 2;

Fig. 7 is a view showing. the means by which-shocks are absorbed, andFig. 8 is another modification.

Referring to the drawings, 10 isthe' frame of an implement, in thisinstance, a windrower; This frame generally comprises angle members,plates and other-nee essary elements which go to'make up machines ofthis nature. 7

A crank member 11 is employed to provide theymeans for reciprocatingthe'sickle and is driven through chain and sprockets and not shownon-the'='drawings, bemg:

must be resolved to one parallel to the axis of the crank 11. The sickleis generally designated" as 12 and extends transversely to the directionoftravel 12 of the imple-- ment as shown in Fig. 1. I

In instances such as that under consideration, a bell crank such as at13 is employed.

bell crank 13 and a pitman 15 connects the sickle 12 with the bell crank13.

The invention will now be described in detail.

Frame 10 has provided thereon parallel plates 16 and 1.7 the latterbeing spaced above the plate 16 as-shown in Fig. 1. Plates 16 and 17 aresecured to frame 10 by rivets 18 and 19. Plates 16 and 17 function assupports for clamping blocks 20 and-21 respectively. Blocks 20 and 21support the" bell crank 13 as'shown in Figs. 1 to 3 and have a slit 22and 23in order that the spindle of the bell crank 18 may be clampedagainst displace-- ment. Blocks 20 and 21' are secured to plates Hand 17by welding in this instance as shown in Figs. 1 to 3 in a mannerspecifically shown in- Fig. 3. 27 and 28 of block 20 are welded to plate16 leaving the other edges free. Block 21 is similarly secured toplate17. Bolts 29 and 30 serve to'draw the halves of blocks 20 and 21together thus clamping the spindle 24 against axial displacement orrotation. 7

As shown in Figs. 1 and 2, the invention comprises mainly an improvedbell crank 13. As mentioned before, bell crank 13 is journalled upon thespindle=24. Bell crank 13 comprises in this instance, an upper crank arm31 and a lower crankarm 32 separated a suitable distance apart on thespindle 24. A reference to Figs. 1 and 2 indicates that the bell crank13 has the crank arms-disposed at an angle of about degrees relative toeach other on the spindle 24. This position is necessary in order toconform to the design of the implement, the

motion of the pitman 14' being at right angles to that of the pitman 15.However, the relative positions of the crank arms can be varied to suitindividual require ments.

Crank arm 31 is of'ca'st steel or a forging, the method of manufacturebeing dictated by the quantity required. A disc portion 33 comprises themain portion-of the hub portion of crank arm 31 and is made ofsubstantial thick ness to assure sufli'cient strength and support forothercommunicates with and lubricates the bushing 35.

Disc portion 33 has extending therefrom a web 37 which is substantiallyat rightangles to the axis of. spindle 24. A pitman-bearing ball portion38 terminates the web 37 and is an integral part thereof.

Disc portion 33 is provided with notches or slots 39 and 40 in theperiphery th'ereof'positioned at degreesapart asshown in Figs. 2 and 4.In thisinstance slots 39 and 40 pass en'tir'ely through the disc portion33';

parallel to the axis ofspindle 34.

Patented Nov. 16, .1954

To complete theassembly a pitman 14 connects the crankll-with the Twoedges Crank arm 31 is so designed that it can be also used as crank arm32 by merely rotating the former 180 degrees about the axis 41 as shownin Fig. 4, and then counterclockwise an angle of 90 degrees as indicatedby arrow 42. Whencrank arm 32 has been thus positioned on the spindle24, the slots 39 and 40 of crank 31 will be aligned with correspondingslots in crankarm 32 as shown in Figs. 1 and 2. The web of crank arm 32is designated as 37 and the bell pitman bearing portion is designated as38. Substantial economies in manufacture are thus possible.

The means of obtaining a unitary assembly is to connect bell cranks 31and 32 by torsional members 43 and 44 which, in this instance, arerectangular in cross section. The relationship of the effective length Lto width W, thickness T and amount of separation D of torsional members43 and 44 is a question of mechanical design involving the skill of oneacquainted with the art, and is dictated by various factors peculiar tothe specific implement involved: The mass of the reciprocating parts andthe rate of oscillation also being deciding factors.

The width W may be such that the torsional members will protrude beyondthe periphery of the disc portion 33 of the crank arms 31 and 32. Thisis a matter of design and within the skill of one acquainted with theart.

Torsional members 43 and 44 should be welded or otherwise secured inthe-slots 39 and 40 so that crank arms 31 and 32 and torsional members43 and 44 form a unitary assembly.

Bell crank 13 is mounted as shown in Fig. 1 with the crank arm 31directed approximately parallel to the axis of the crank member 11. Thepitman 14 connects the crank member 11 with the ball portion 38. Thecrank 32 is directed forwardly in the direction of arrow 12 and at rightangles to the direction of reciprocation of the sickle 12. Sickle 12 hasafiixed thereto a ball pitman bearing 45, and the sickle pitman connectsball 45 and the ball pitman bearing portion 38.

On inspection of Fig. 1 it will appear that rotation of crank member 11will effect reciprocation of sickle 12. The sudden shocks owing to thechange .in direction of movement of the several members will besubstantially absorbed by a combined twisting and bending of the torsionmembers 43 and-44. This effect is graphically shown in Fig. 7 whichshows torsion member 43 in its twisted state resulting from a shockinduced by reciprocating forces. A substantial amount of the shock hasbeen absorbed before the motion is reversed. The angle 46 of Fig. 7 isless than that between the crank arms 31 and 32 when the sickle 12 is atrest. Torsion member 44 is not shown in Fig. 7 in that the showing ofmember 43 is sufficient to explain the function of the invention, bothmembers 43 and 44 being subjected to like forces.

Fig. 6 shows a modification in-which the disc member 48 has cylindricalrecesses formed on theperiphery thereof, other details of the'crank arm50 being similar to the crank arm 31 shown in Fig. 2. Torsion members 52and 54 are of cylindrical cross section and are secured by welding inthis'instance, to the disc member 48 in the recesses above mentioned,the welding, being done at points on each side of the recesses as at 56and 58. A second crank arm is provided similar to arm 50 and theassembly completed as in the manner shown in Fig. 2.

Fig. 8 shows a simplified 'modification of the invention. In thisinstance the hub portion 60 has no notches in the periphery thereof: Thedesign of crank arm 62 being otherwise similar to that of crank arm 31.

Torsional members 64 and 66 are tangentially located on the periphery ofthe hub portion 60 as shown in Fig. 7. and welded or otherwise securelyfastened thereto to form a unitary bell crank.

Summarizing the invention it will be understood that shocks incident toreciprocating the sickle 12 under normal conditions will result ininjurious shocks to the actuating mechanism. When the bell crank 13which embraces this invention, is employed the reciprocation will set upa series of relative angular oscillations of the crank arms 31 and 32.These oscillations will be resisted by the torsional members 43 and 44of Fig. 2, but owing to the natural resiliency of the members 43 and 44there will be a slight relative rotation of arms 31 and 32 about theaxis of the spindle 24, resisted only by the resistance to bending ofthe members 43 and 44'. The slight relative rotation of arms 31 and 32and the consequent bending or flexure of members 43 and 44 will besufiicient" to absorb the more substantial shocks tending to injure themechanism;

The above being a complete description of an illustrative embodiment ofthe invention, what is claimed as new and desired to be secured byLetters Patent of the United States is:

1. In a shock absorbing sickle actuating means for a harvester having aframe, and a spindle fixed uprightly against rotation on said frame, theimprovement comprising a bell crank on said spindle having an upper anda lower crank arm, each of said arms provided with bushings andindependently journalled on said spindle and spaced apart thereon, eachof said crank arms provided with hub portions concentric with the axisof said spindle and a pair of slots disposed on the periphery of each ofsaid hub portions at diametrically opposed positions, correspondingslots in said hub portions being mutually aligned, a pair of torsionmembers extending betweensaid hub portions and secured unitarily attheir extremities in said slots to connect said crank arms for limitedrelative shock absorbing rotation independently of said spindle bydistortion of said torsion members, said torsional members protrudingbeyond the periphery of said hub portions.

2. A shock absorbing bell crank for actuating a sickle on a harvester,the improvement comprising a spindle fixed against rotation on saidharvester, and supporting said bell crank, said bell crank comprisingupper and lower radially extending crank arms, each of said arms beingindependently journalled on said spindle and axially spaced apartthereon, each of said arms provided with a pair of axially extendingslots on the periphery thereof, the slots of each of said arms beingaligned with corresponding slots of the other arm and a pair of torsionmembers connecting said arms and permanently fixed in said slots toallow limited relative shock absorbing rotation of said arms freelyabout said spindle by distortion of said torsion members.

3. A shock absorbing bell crank for actuating a sickle ona harvester,comprising a spindle fixed against rotation on said harvester andsupporting said bell crank, said bell crank comprising a pair of crankarms, each being independently journalled on said spindle and axiallyspaced apart thereon, each of said arms provided with a pair of axiallyextending slots on the periphery thereof, the slots of each of said armsbeing aligned with corresponding slots of the other arm, and a pair oftorsion members permanently connecting said arms and terminating in saidslots to allow relative shock absorbing rotation of said arms freelyabout said spindle by distortion of said torsion members, said torsionalmembers lying in radial planes.

4. A shock absorbing bell crank for actuating a sickle on a harvester,comprising a pivot means for said bell crank, said bell crank having apair of crank arms, each being independently journalled on said pivotand axially spaced apart thereon, each of said arms provided with a pairof axially extending semi-cylindrical notches on the periphery thereofthe notches of each of said arms being aligned with correspondingnotches of the other arm, and a pair of cylindrical torsion membersconnecting said arms and permanently secured in said notches to allowlimited relative shock absorbing rotation of said arms freely about saidpivot.

5. A shock absorbing bell crank for actuating a sickle on a harvester,comprising a fixed pivot means for said bell crank, said crank having apair of crank arms, each being independently journalled on said pivotand axially spaced apart thereon, each of said arms being provided witha hub portion normal to the axis of said pivot and co-axial therewithand a pair of torsion members permanently and integrally connecting saidhub portions and spaced adjacent the periphery thereof and forming anintegral unitary assembly allowing limited relative shock absorbingrotation of said arms freely about said pivot means.

6. A shock absorbing bell crank for actuating a sickle on a harvester,comprising a fixed pivot means for said bell crank, said crank having apair of crank arms each being independently journalled on said pivot andaxially spaced apart thereon, each of said arms being provided with ahub portion surrounding the axis of said pivot means, at least onetorsional member intermediate said hub portions and secured integrallyadjacent the peripheries thereof resulting in a unitary assembly limitedto relative rotation of said arms freely about said pivot means bybending and distortion of said torsional member.

7. A shock absorbing bell crank for actuating a sickle on a harvester,comprising a fixed pivot means for said bell crank, said crank having apair of crank arms each being independently journalled on said pivot andaxially spaced apart thereon, each of said arms provided with a hubportion, a torsional member intermediate said hub portions and securedintegrally about the peripheral surface thereof resulting in a unitaryassembly limited to relative rotation of said arms about said pivotmeans to that permitted by the bending and distortion of said torsionalmember.

References Cited in the file of this patent UNITED STATES PATENTS NameDa Number Number Name Date Bacon Nov. 9, 1869 Crowther Feb. 8, 1876Morris Apr. 19, 1898 Trufant Jan. 20, 1914 Hobbs July 10, 1917 WelkerJan. 13, 1925 Dante Dec. 8, 1931 Stone Feb. 9, 1932 Fulton Apr. 24, 1945FOREIGN PATENTS Country Date Norway Dec. 27, 1943 Great Britain Oct. 22,1906 Great Britain July 3, 1924

